Libraries GuideChapter 4: Design Elements (CAPTURE_SPARTAN2 to DECODE64)
CY_MUX
2-to-1 Multiplexer for Carry Logic
XC3000
| XC4000E
| XC4000X
| XC5200
| XC9000
| Spartan
| SpartanXL
| Spartan2
| Virtex
|
|---|
N/A
| N/A
| N/A
| Primitive
| N/A
| N/A
| N/A
| N/A
| N/A
|
CY_MUX is used to implement a 1-bit high-speed carry propagate function. One such function can be implemented per logic cell (LC), for a total of 4-bits per configurable logic block (CLB). The direct input (DI) of an LC is connected to the DI input of the CY_MUX. The carry in (CI) input of an LC is connected to the CI input of the CY_MUX. The select input (S) of the CY_MUX is driven by the output of the lookup table (LUT) and configured as an XOR function. The carry out (CO) of the CY_MUX reflects the state of the selected input and implements the carry out function of each LC. When Low, S selects DI; when High, S selects CI.
Inputs
| Outputs
|
|---|
S
| DI
| CI
| CO
|
|---|
0
| 1
| X
| 1
|
0
| 0
| X
| 0
|
1
| X
| 1
| 1
|
1
| X
| 0
| 0
|
The following figure depicts the application of the CY_MUX for a 4-bit adder. Also shown are the associated FMAP symbols and the CY_INIT function.
Figure 4.53 CY_MUX 4-Bit Adder Schematic XC5200